string::token::shell(3) Parsing of shell command line


package require Tcl 8.5

package require string::token::shell ?1.2?

package require string::token ?1?

package require fileutil

::string token shell ?-indices? ?-partial? ?--? string


This package provides a command which parses a line of text using basic sh-syntax into a list of words.

The complete set of procedures is described below.

::string token shell ?-indices? ?-partial? ?--? string
This command parses the input string under the assumption of it following basic sh-syntax. The result of the command is a list of words in the string. An error is thrown if the input does not follow the allowed syntax. The behaviour can be modified by specifying any of the two options -indices and -partial.
When specified option parsing stops at this point. This option is needed if the input string may start with dash. In other words, this is pretty much required if string is user input.
When specified the output is not a list of words, but a list of 4-tuples describing the words. Each tuple contains the type of the word, its start- and end-indices in the input, and the actual text of the word.

Note that the length of the word as given by the indices can differ from the length of the word found in the last element of the tuple. The indices describe the words extent in the input, including delimiters, intra-word quoting, etc. whereas for the actual text of the word delimiters are stripped, intra-word quoting decoded, etc.

The possible token types are

Plain word, not quoted.
Word is delimited by double-quotes.
Word is delimited by single-quotes.
Like the previous types, but the word has no closing quote, i.e. is incomplete. These token types can occur if and only if the option -partial was specified, and only for the last word of the result. If the option -partial was not specified such incomplete words cause the command to thrown an error instead.
When specified the parser will accept an incomplete quoted word (i.e. without closing quote) at the end of the line as valid instead of throwing an error.

The basic shell syntax accepted here are unquoted, single- and double-quoted words, separated by whitespace. Leading and trailing whitespace are possible too, and stripped. Shell variables in their various forms are not recognized, nor are sub-shells. As for the recognized forms of words, see below for the detailed specification.

single-quoted word
A single-quoted word begins with a single-quote character, i.e. ' (ASCII 39) followed by zero or more unicode characters not a single-quote, and then closed by a single-quote.

The word must be followed by either the end of the string, or whitespace. A word cannot directly follow the word.

double-quoted word
A double-quoted word begins with a double-quote character, i.e. " (ASCII 34) followed by zero or more unicode characters not a double-quote, and then closed by a double-quote.

Contrary to single-quoted words a double-quote can be embedded into the word, by prefacing, i.e. escaping, i.e. quoting it with a backslash character \ (ASCII 92). Similarly a backslash character must be quoted with itself to be inserted literally.

unquoted word
Unquoted words are not delimited by quotes and thus cannot contain whitespace or single-quote characters. Double-quote and backslash characters can be put into unquoted words, by quting them like for double-quoted words.
Whitespace is any unicode space character. This is equivalent to string is space, or the regular expression \\s.

Whitespace may occur before the first word, or after the last word. Whitespace must occur between adjacent words.


This document, and the package it describes, will undoubtedly contain bugs and other problems. Please report such in the category textutil of the Tcllib Trackers []. Please also report any ideas for enhancements you may have for either package and/or documentation.


bash, lexing, parsing, shell, string, tokenization


Text processing